Activation of clay by acid treatment, aging in inhibited oil, and calcination



Uni ed. T"

2,925,393 .7 scmxms F CLAY BY 1 ACID TREATMENT, AGING IN mrnsrrun om,CALCINATIQN Wright. Wesley Gary, Princeton, N.'J. ,-Ia ssignor to Min--ferals &-'Chemicals' Corporation of-America, Menlo Park,NJ.,acorporationofMar'ylau l- I No Drawing. Ap iicationrune'f 1957 1.

' t I Serial No. 6 64 ,167. I

110mm.- tci. 252-450 This invention relates to the: preparation'ofadsorptive hydrocarbon cracking processes are employed,as is well known,for the purpose-of converting petroleum hydrocarbons -to gasoline:

In fixed bed cracking, the hydrocarbon vapors are p-assed"through astationary bed of catalyst particles,

saidmasses-io high quality adsorptive contact masses especially suitableas hydrocarbon, cracking catalysts.)

Ihe process disclosed in' the aforesaid co-pending application of Weirand Robinson, as pointed out therein, represents aradical departurefromthewelhknown prior art acid leaching methods. comprising'essentiallythe basic steps of reacting the-clay. with dilute acid, usually;- dilutesulfuric acid toiconvertpart. of said clay to water soluble form andthen leachingior washing substantially allof ,the result ing watersoluble material from the clay-aeid reaction product with water, leavingbehind, a residue from which is obtainedthe. final product and which isof different chemiealgcomposition than 'the 'starting clay sincea;portion of .said=clay has been removed in the leaching .SteDg In thenovel process of the co-pending Weirand Robinson application,- on theother hand, the clay is reacted with sulfuric acid andthen theclay-acidmixture-is calcined .to decompose water soluble products of thereaction, whichproducts correspond substantially to those leached fromsaid mi'xtupe in the priorpart acid leaching method, and to convert saidmixture to a material suitable foradsorptive contact purposes whichmaterial is substantiallyjhe .same; in chemical composition asthestar-ting 1clay,. on a yolatile free basis but of enhanced'activitytTheprior art acid leaching processes can be ,considered wet-methods ofclay activation since while in moving bed cracking processes,as'exernplified by Thermofor catalytic cracking (T.C.C.) -and Houdriflowoperations, the-catalyst particles gravitate towards the'base of thereactor from whence theyare conveyed through-regenerators and back tothe top of the reaction zone for another pass therethrough. The Houdrifiow process differs from the T.C.C. process in the manner ofconveying regenerated catalyst particles forrecirculation through thereactor, a gas lift being used in the former case and elevators in the'latter. Catalyst particles for fixed and moving bed processes arerelatively coarse, ranging in size from about IO-mesh to about4-mesh,-.and

' usually in the form of pellets or fbeadsf? To be acceptable, acracking catalyst should possess adequate activity and hardness and itshould exhibit'satisfactory catalyst life while in'service. The reasonfor needing good cracking activity. in a'catalyst is self-evident,

and a sufiicient degree of hardnessis necessary therein to minimizeattrition of the catalyst particles fduringtheir utilization. Attritionis detrimental since it resultsin loss of active catalyst as fines,whichare carried out in the effluent vapor stream, with attendantincrease in operating cost. Catalyst life, as the name implies, simplyrefers to the period of economic usefulness of a catalyst inservice. a

In a co-pending U.S. patent'application of Serial No.

v499,515, filed AprilIS, 1955, by James V. Weir and Alfred J. Robinson,there is disclosed animproved process for the preparation ofadsorptivecontact masses from-naturally occurring acid-activatable clays andparticularly from kaolin clays,

clay and sulfuric acid together to produce a plastic mass, formingappropriately sized masses, as for example by "extrusion, from saidplastic mass; aging the clay-acid ing kaolinite. as, the chief mineralconstituent.

In' its preferred embodiment, the; process of said co-pendingapplication involves mixing formed thereinduring the aging and tothereby convert they'entail an;aqu eous leaching step, whereastheprocess ofthe co-pendingNVeir-and Robinson application can beconsidered'a dry'onein that it doesnot require'aqueous leaching of theclay-acidfreaction product'forremoval' offitswater.solublesportion; t at Thepresent invention, is'the result of my discovery of a preliminaryconditioning treatmentjof the hydrocar-v bon liquid; in which ,theclay-acid mixture is aged, as taught in the co-pending application ofWeir and Robin; son, whereby a substantial improvement in hardness offinal contact masses isattained; Thus contact masses, produced accordingto the Weir and Robinson process of the aforesaid co-pending patentapplication in which the aging iscarricd out in a hot hydrocarbon liquidwhich has previously been conditioned, as taught herein, will be foundto be high quality adsorptive contact masses of hardness substantially,superior to that of contact masses produced inqthe same manner.exceptgaged in a hydro,- carbon liquid which has not been subjected tothe afore said preliminary conditioning treatment. Accordingly," it isone objectof the present inventio 'to provide an improved process forpreparing adsorptive contactmasses from clay. v A further object of theinvention is to provide an improved process for preparing hydrocarboncracking cat,- alysts'of superior hardness. I r Other objectsandadvantages of the invention will be apparent from the descriptionthereof which follows.

As previously noted; the process of the present invention is intendedprimarily for use on kaolin clays,--by which is meanftho'se naturallyoccurring clays contain- The approximate chemical composition ofkaolinite is represented by. the formula: Al O .2SiO .2H O. The weightratio of'SiO to Al O ,'indicated by this formula, is 1.18 andkaolin-claysnormally 'possess SiO /Al O ratios of from 1.1.0 to 1.5. I-x While I prefer touse degritted raw clay (that which has been'refinedonly to the extent .that grit, foreign bodies and clots.of undispersedclay have been eliminated) as a starting material in the' process, Iwish"to have .it clearly understood, that the invention is notlimited totheltreatment of such a product. Clays which have received otherpreliminary treatments may still be amenablejjo processing in.aceordancemwithlteachings Q an er; Feb. 16, 1969 herein. Examples'ofpreliminary treatments falling withstartingclayshonld preferably not beso'high as to make too diluent a mixture of clay and acid for optimumhandling under the conditions of the particular processing involved. Ihave :obtainedexcellent results using a starting clay of about 14percent V.M. with moderate dosages of concentrated sulfuric acid. Byvolatile matter (V.M.) is meant that part of the clay which would beeliminated by heating said clay'at 'a temperature of about I700 F. tosubstantially constant weight. The weight of -the clay without itsvolatile matter is referred to as the 'volatile free (ViFQ) weight ofsaid 'cl'ay.

In putting the process'of "my invention into practice, a 'naturallyoccurring clay, as for example kaolin clay, "andsulfuriciacid are'first mixed to anappearan'ce of Homogeneityin any apparatus suitablefor the purpose, as forexample' -a pug-mill. Theclay-acid mixture isthen extruded to form pellets, or otherwise shaped into masses withinthe desired size range. Next, the pellets or shaped masses areimmersed-and aged in a hydrocarbon liquid, which has been previouslyconditioned in the manner hereinafter disclosed, under such conditionsof-time and temperature as to bring about"substantiallycomplete reactionbetween the clay-a'ndthe acid. This aging of'the pellets,'or othershape' d' masses ''may be accomplished, for example,in a screw conveyorby conveying said pellets 'or ma'sses, while'irnmersed inthe hydrocarbonliquid at the desired temperature level, therethroughat a rate such asto afford adequate time for substantially complete reaction between clayand acid.

The aged pellets are finally subjected to calcination treatment, toeffect desulfationthereof, with'attendant conversion of said pellets tohigh-quality adsorptive contact'masses particularlysuitabl'e ashydrocarbon crackingcatalyst. The term pellets, as used aboveand-hereinafter throughout the specification and claim, except asotherwise indicated, is'inten'de'd to include within its meaning notonly extruded pellets but other suitably shaped masses within the propersize range which have been formed by methods wellknown to those skilledin the art.

I prefer to use concentrated sulfuric acid, such asthe commerciallyavailable 66 'B. (about 93 percent H 80 grade, for the-clay-acidreaction of our process, water being added, if-necessary, to facilitateease of 'pugging, or otherwise mixing, the ingredients. "However, anystrength acid consistent with proper plasticity of mix for the dosageemployed "can be used within the scope of this invention. I prefer touse iacid dosages from about 60'percent to about 100-percent inourlprocess, acid dosage being defined astheweight of 100-percent acidper weight of volatile free clay expressed on a percentage basis.

Although acid dosages much lower than 60 percent, down to as low as20pe'rcent in-fact, can-beuse'd' in the process with some benefit,-theclay conversion gradually falls off with decreasing dosage untilineffectual levels are reached. With the 'lower dosages of acid,it hasbeen found nece'ssaryto have-higher water/acid'ratios inthe 1 ferredrange of acid dosage has been given as that from about 60 percent to"about percent, dosages higher than 100 percent can be used within thescope of the invention so long as a workable mix is obtainable in theprocess. Approximately percent dosage represents the amount of acid thatwould theoretically be required for substantially complete reaction withan average kaolin clay, although amounts in excess of this can be usedwithin the scope of the invention.

As previously indicated, the mixture of clay and acid is preferablyformed into masses of appropriate size by extrusion or equivalent methodbefore the aging'step' of our process. The forming operation can .beperformed by extrusion, pilling or any equivalentmethod known to thoseskilled in the art; the preferred method being extrusion by means of'a'n'auger'mill *or'extruder. For best results in extrusion, the V.M. of themix should be between'abou't 30 and about :65 percent,with-theflreferredrange being from 501to '55 percent.

The hydrocarbon liquid in which the :pellets are aged should be onewhich is substantially non-reactiveewith sulfuric acid, at the agingtemperature level, although minor amounts of matter capable 'ofreactingwith-the acid can be tolerated therein. These hydrocarbon liquids shouldpreferably'have low vapor pressures at'theaging temperatures, but Idognotwish to exclude the possibility of using lower boiling materialsin conjunctionwith a condenser system to prevent loss'of vapors.Examples ofre'adily available hydrocarbon liquids which are suitable forthe process aresaturated aliphatic higher molecular weight hydrocarbonswhich :have been treated with sulfuric acid for removal of sulfonatablecomponents such as, for example, certain white mineral oils. Kerosenecan also beused as-the aging medium if condenser-systerns are available.

Optimum temperatures 'for 'our'oil aging fall between the limits ofabout 220 F. and about 400 'F.-and optimum times within the rangefromyabout l to about24 hours, with the times required depending on :thetemperatures used. I prefer to age within the temperature range from27.5 to 32-5 F. for a period of from-about 1 to about 5 hours. Whenaging temperatures become too high, the clay-acid reaction proceedsrapidly-and the finalproduct is excessively soft. When agingtemperatures are too low, the product is'also soft but in this case thecause seems to stem from insuflicient .reajction due to a very slowreaction rate.

As previously indicated, the hydrocarbon liquid in which the pellets areagedissubjected to a preliminary conditioning treatment for the purposeofeffectingsubstantial improvement in the hardness of the final contactmasses. Although the pellets can be aged in hydrocarbon liquid which hasnot been subjected to saidpreliminary conditioning treatment the finalcontact masses willibe found to be of only mediocre hardness bycomparison with adsorptive contact masses produced in the same manner,except for the preliminary conditioning of thetoil in which they areaged. The preliminary conditioning treatment of the present inventioncomprises incorporating a small amount of an antioxidant compound insaid hydrocarbon liquid prior to using said hydrocarbon liquid 'as anaging mediumin the present invention. The antioxidant may be added tofresh oilused as the aging medium for clay-acid masses in the-initialstart-up of a the incorporation of an antioxidant-in-the hydrocarbonliquid-prior to; its reuse as .;an aging. mediumv -is necessaryto'ehtain the benefitsofthe invention. 'lThisisso bfecause thehydrocarbon liquiddeteriorates; in: some unknown-rway in respect toperformancejin producing 'mas'ses iof ultimate satisfactory hardnesswhen said hydrocarbon liquid stands without thepresence of clay and acidat elevated v temperatures. Bythese practices'the oil will include. atall times sufiicientantioxidant to maintain the' jp'rop'er level of oilconditioning to assure the production of'uniformly hard pelletsthroughout the processing- The conditioned hydrocarbon liquids maybeused substantially indefinitely as 'aging mediumsifor clay-acid 'pelletswithout deterioration, insofar as theirhardening effect on the finaladsorptive masses are concerned provided that said hydrocarbon liquidsare held at elevated temperatures with. clay and acid thereinatalltimes, It isno tleissenposes be previously conditioned. as taughtjhe'rein; small quantities'of fresh hydrocarbon liquids which have notbeen so conditioned. may be used, in normalmake-up quantities withsubstantially no lowering or the hardness .of-the finalpellets .or otherdeleterious afterefiectsl, J

Suitable antioxidizing agents or antioxidants to con'dition thosehydrocarbon liquids within th'e 'pur'view'of my invention includenon-metallic antioxidants'which are stable and have low vapor pressuresat the elevated temperatures to which they are subjected whenincorporated in the hydrocarbon liquid and which leave no "deleteriousresidue on the pellets or massesrafter thecalcination there- .tial thatthe hydrocarbon liquids usedZf r-rnakemp" purj gozaeces,

the aromatic nucleus eet tofsterically hinder activity of the compoundare ofsuperior characterfor the purposes of this invention. Thesecompounds which maybe prepared by reacting phenols with low molecularweight olefins have outstanding inertness, lack of toxicity,oilsolubility and'potency.j Useful hindered phenols include isomers ofbutylated hydroxy toluene, particularly 2,6- di-tertiary butyl-paracresol, isomers of butylated 'hydroxyanisol, such as4-methyl'-2,6-ditertiary butyl methoxyben'zene, and ;2,'6'-di-tertiaryamyl-para cresol. The hindered phenolic antioxidants may also be usedamines,and'higher fatty ;acids, j 1 Another class i of antioxidantssuitable forthe purposes "of'theinvention include" aromatic aminoantioxidants,

' which are similar to phenolic antioxidants, except that the freehydroxyl groups iii the benzene nucleus have been replac'ed wholly or inpart by amino groups. 'They are represented typi9al1ybyfp-amino phenol;and' hydro'xy f stitutedjin the amino "group to increase the oilsolubility, .25

naphthyl amine,the,former of which oxidizes reversibly ftoquin'oniminein a manner comparable to that of hydroquinone. Among the"more useful antioxidants of this class are those in which an organicconstituent is sublower the vapor pressure and increase the stability ofv Ithe molecule; Y The requisite configuration for this class of. It hasbeen found that antioxidantsincluding metallic or non-volatile inorganicconstituents either poison the catalyst, in the case ofmetalli'cconstituents such as iron,

or in the case of alkali or alkaline earth constituents such as sodium,deposit ,saltso'nthe, pellets which act as flux-- ing agents during thecalcination of the aged pellets."

' It has been found that certain. aromatic compounds in which oxidationis'reversible areparticularlyefiective as conditioning agents for thehydrocarbon liquid for the purposes of the invention, such compounds-being broadly classified as phenolics and p-amino phenols.

Among the phenolic antioxidizmg agents capable of reversible oxidationare those polyhydroxylaromatic compounds with ortho and para hydroxylgroups, the prototype of which is hydroquinone .(p-dihydroxybenzene)which oxidizes reversibly to quinone. Others in this category includepyrocatechol (catechol, o-dihydr'ox'ybenzene) and pyrogallol(1,2,3-trihydroxybenzene). However, other substituted aromatics which donot have 'at least two directly substituted hydroxyl groups areeffective agents if their structure-is comparable "to that of the orthoand para hydroxyl compound in respect to electronic configuration andmobility; these aromatics may be substituted benzenes, condensedaromaticstructures containing a benzene ring oreven heterocycliccompounds and will be hereinafter referred to as quasiortho and parapolyhydroxy phenols. This classification includes3,4-methylene-dioxyphenol in which 'one hydroxyl group is para to anoxygen atom attached to the benzene nucleus and 3-phenyl isocoumarone,which has an hydroxyl group in the enolic form. In other quasicompounds,for example, the'tocopherols,-a heterocyclic oxygen para to a freehydroxyl-group gives the requisite electronic configuration.Alpha-naphthol has the configuration of an efiective ortho'cornpound;Frequently partial substitution in the aromatic ring' is madeto-Idevelop oil solubility, loweredtoxicity, improve heat stability andlower vapor pressure. Such substitution has jis cornparable to thatoutlined for phenolic antioxidants which oxidize freversiblyQSuitableantioxidants in this classification Qincludef p-benzyl'aminophenol," peis'obutyl- "aminophenol,'"' p-n-but'ylaminophenoland p-di-n-butylaminophenol.

1 Other useful antioxidantsare those formed bytheconcompoundthatcontains only'C, .H plus S,.the S being 'directly attached to thearomatic ring(suitable species no'harmfulefiect on the'antioxygenicactivity unless cornplete substitution destroys the activity of thecompounds by restricting electron mobility, For example, a preferred'species of antioxidants for the purpose herein set forth are alkylatedpolyhydroxyl or quasi-polyhydroxyl compounds, such alkylated compoundsdisplaying improved oilsolubility and lowered vapor pressureov'er theirnonalkylated counterparts and includingfbutylated hydroquinone, t-arnylhydroquinone and t-bt'ltyl catechol';v It

has been found that the so-called hinderedaphenolsf I in which thereactivity of the phenolic group is reduced; T by thepresence' of aplurality of 'tertiaryalkylj groups: in

re A-and B-thionaphthQl, diphenyl disulfide. thiocresoidimercapto-biphenyl, naphthyl disulfide); compounds of the general,formula (ROSCSC H O, where R.is an 'alkyl or aralkyl radical,such'asdixanthylethyl ether, compounds'of the general formula in which Rrepresents'an' alkyl, aryl or aralkyl' hydrocarbon group; compounds ofthe general formula RHNC H NO, in which R represents an alkyl or anaralkyl radical, aminodiphenyl amines in which one phenyl nucleus isamino-substituted and the other is alkyl substituted'alkyl aromaticdiethers containing two alk oxy groupsattached to anarornatic nucleus,at leastone al-.

koxy group containing a tertiary alkyl radical of 4 to 5 carbon atomsyortwo alkoxy groups attached toan aromatic'nucleu's para to each other;aliphatic diamino substituted diaryl methanemompounds, such astetramethyl diamino diphenyl methane. I

It will be, understood that the choice of antioxidant added to trash, ordeteriorated used oil'to render that oil usefulffor the purposes setforth willjdepend not'only on thehpa'rticular'composition of oil usedinthe aging process, butals'o on the temperatures maintained duringtheagingproeess and the time duration in which elevated J temperaturesare maintained, "whereby, the thermal js'tabilitylcharacteristics andthe vapor pressurebf the antii'joxidant is a fajct or'in determining theselection. The,

'optimumJamount of antioxidant relative to the hydrocarbon oil used"likewise is subject to wide variation and it should be determinedexperimentallyi Thereis'iiof'empirical formula or theory on which tobase {this {choice in admixture withother compounds such as aromatic,

because the correlation between the anti x d tipn p ential of anycompound and its ability in the system to insure .adequate pellethardness is obscure. However, it is a fairly safe procedure to employ aratio of antioxidant to any make-up oil in which it is incorporatedsubstantially equal to the ratio of antioxidant to unconditioned oilused preliminary to aging the clay-acid masses in the oil.

At any stage of the process, the .criterionof satisfactory oilconditioning is the determinationof satisfactory ultimate hardness ofpellets aged in the oil at that particular stage. Where at any stageftheinherent ability of the clay-acid masses held at elevated temperaturesin the hydrocarbon liquid to condition the oil is inadequate, this beingmanifest by unsatisfactory ultimate-hardness of pellets aged with suchil, then an antioxidant should be .added. This situation will prevailwhen initiating the aging process using fresh hydrocarbon liquid orhydro carbon liquid from previous aging runs which has been .madeavailable for re-use after asliutdovvn'of the aging apparatus orpossibly on adding make-up oil, particularly when such make-up oil isadded in large quantities ,to

the system.

In general from about .010 percent to about .100 percent of anantioxidant, based onthe weight ,of uncon- .desulfation, .l .havefoundthat for bestresults the temperature .shouldbe between the limitsof about '900 and about 1600 F. and the calcination time should,preferably be not greater than about 24 ho urs. The temperature and.times ofcalcination will depend to a large extent on the atmospherewithin the furnace in which the pellets' are calcined. While .I do ,notwish to exclude calcination temperatures outside of the range disclosed,I would like to make clear that at temperatures much below 900 F. thealuminum sulfate decompositionrnay be incomplete and that temperaturesabove 1600 F. may result in lowered activity of thefinal product.

It is within the scope of the inventionto incorporate not. more thanabout percent, on a total Weight of mix basis, of-a combustible fillerinto theclay-acid mixture of our process priorutoformationof,thesaidgnixture into shaped masses. This filler, among other things,serves to increase the porosity of the;final catalyst since it iseliminated duringthe :calcinationstep leaving voids behind. Examples offiller suitable for the purpose are wood flour, corn meal, sawdust,carbon .andthe like.

Following, are examples which. are included herein for the purpose ofdemonstrating the improvement in hardness attainable by-means of .thenovel conditioningpof hydrocarbonliquids by incorporationofsmall amountsof antioxidants therein prior toHusingthem as-aging mediums in thepresent process. These .examplesvare for purposes of. illustration only.and they shouldnotbe ,con-

, strued as limiting the invention to anypartciular embodimentsdisclosedtherein.

Example' l This example. is acontrol test to indicate the.,degree ofhardness attainable when clay-acid pellets are aged Georgia kaolin clayis mixed with sulfuric acid ofabout 93.2 percent concentration, theamount of acid used bein a hydrocarbon liquid whichlhasnot beenconditioned.

ished stainless steel ball bearings, each of 'liquid product from thecracking test is collected at a temperature of 60 F. Catalytic activityis measured as the volume percent yield of gasoline on a no-loss basis(N.L.B.,g asoline yield) and given as the volume of 4 10 F. endi'pointgasoline distilled from the aforesaid cracked product, corrected for 100percent recovery, expressed as a percentage of the volume of gas oilcharged. 'As part of the Cat- A test, the weight of coke deposited onthe catalyst, weight of gas produced, and gas specific gravity aredetermined. The coke and gas weigh-ts'are expressed as' percentages ofgas oil charged. Two Cat-A cycles are run with only the data from thesecond cycle being used since experience has shown these data to besound. In general the ratio of N.L.B. gasoline yield to coke yieldshouldexceed about 9/ 1 or 10/1; gas gravity should be atleast l.2 or higher.

The Cat-A test on the pellets of this example reveals an N.L.B. gasolineyield of about 32 percent, a ratio of :NLB. gasoline yield to coke yieldexceeding 10/1, and a gas gravity higher than 1.2.

v 7 These results, as one skilled in the art will recognize, show thatthe pellets ,of the present example are of excellent quality insofar asactivity and selectivity is concerned.

The pellets produced in this example may be tested for hardness by aball mill procedure, as described hereinbelo-w. The test for hardnesscomprises a procedure in which a sample of catalyst pellets is firstseparated into three fractions by screening through 3-mesh and S-meshsieves until about 200 gramsof the 3/5 fraction is obtained. The 3/5fraction is then heat treated at 1050 F. by passing bone dry air over itfor three hours. The heat treated material is poured into a tared 100cc.graduate to the 80 cc. mark, with tapping to gently pack the particles.The weight of the 80 cc. of catalyst particles is determined and theyare then placed in a stainless steelcylindrical container with fourpolinch diameter. The container is closedtightly and rotated about .itslongitudinal axis at about 80' rpm. on a roller arrangement, for aboutone hour. 0 After therotation of the container has beenstopped, thecatalyst solids therein are screened on. a.6.-i n'esh sieve and theirhardness is calculated as ,the percentage of total sample (ie the 80.cc.) .weight represented by the plus-.6-mesh fraction of the finalmaterial. The )pellets of the present examplepossess a hardness of fromabout to about percent as determined ,by the above-described ball millprocedure. For comparative purposes the commercial catalyst Filtrol .62,which is prepared from subbentonite clay, when measured by the aforesaidball mill method is found to, possess ahardness of 90 percent.

Example [I ParanoxAAl, marketed andsold by 'Enjay Corporation,

Inc. Raranoxl44l is;the;2 and ,3 mixture of isomers of di-tertiarybutylpara cresol.

. G eorg'ia .kaolin clay ismixed with sulfuric acid of about 23,2.percent concentration, the amount of acid ,;used. beingequivalent toadosage, of about percent.

extrusion. The extruded'pelletsare-aged in the whiter mineral oilhavingp025 percent'by weight-of Paranox 441 incorporated therein,maintained at a temperature ofabout 300 F., for a period of about 3hours. The aged pellets are calcined in an atmosphere of steam and hotflue gases containing reducing components until they have beensubstantially desulfated; during" which operation they reach a maximumtemperature of about 1 430 F;

The 'desulfated pellets tested by the Cat-A procedure are substantiallyequivalent to those of Examplelin catalytic activity. Samples of thepellets tested for hard:

found to possess hardnesses of well above 90 percent and, in fact, ashigh as 97 or 98lperc ent. Thus the pellets of the present'example havebeen shown to be superior to Filtrol 62 in this respect. p

Comparison of the hardnesses of the pellets of the present example withthose of-the pellets of Example I clearly shows the unexpectedimprovement in hardness 10 '7 w I attributable to my novel aging liquidconditioning treatment. I

Iclaim: A process for the preparation of cracking catalyst pellets fromrkaolin clay including the steps of mixing the kaolin clay with about20m 130 percent dosage of sulfuric acid of a concentration within therange from about 50 percent to fuming sulfuric acid; forming pelletsfrom the resulting mixture of clay and acid; aging the pellets forabout1 to 24" hours by immersing them in white mineral'oil containing a minorquantity of di-ter- I tiary butyl-para cresol and maintained within thetem- I ness by the previously described ball mill procedure wereperature rangesfrom about 220 to about400 F.; and calcining the aged;pellets within the temperature range of about 900 to about 1600 F. for aperiod of time not greater than about 24 hours.

References Citedin the file of this patent. UNITED STATES PATENTS2,787,599 Belden Apr 2, 1957 Baylis t Nov. 11,1930

